Neuropeptide Y (NPY) is a central and sympathetic neurotransmitter with pleiotropic activities ranging from appetite control to cardiovascular function. Over the last decade our lab focused its research on NPY regulation of vascular tone and made some important discoveries e.g. that NPY is a stress-activated testosterone-dependent vasoconstrictor acting via Y1 receptors (RS)- a notion now supported with development of hypertension in male rats by over-expressing NPY. During the previous grant period we have identified yet another bioactivity of NPY-as a vascular growth factor. NPY stimulates proliferation of vascular smooth muscle (VSMCs) and endothelial cells (for which it is angiogenic), and neointimal proliferation in vivo, at concentrations below vasoconstrictive and via multiple Rs: Y2/Y5 or Y1/Y5 or Y1/Y5 Rs, depending on NPY concentration. Each of these Rs is Gi-coupled but possibly to different adenylyl cyclase (AC) isoforms. Since VSMCs and rat carotid arteries possess extremely low abundance of NPY Rs, NPY's actions require their up-regulation-a process mediated by NPY itself and beta-adrenergic R (betaAR) agonists. In this renewal application, we propose to focus on interactions between betaARs and NPY-induced vascular growth. We found that pre-exposure of VSMCs to isoproterenol induces Y1, Y2 and Y5 Rs, and markedly augments NPY's mitogenic effect. The overall hypothesis is that pre-conditioning of vessel wall by betaAR activation- desensitization up-regulates NPY Rs and/or post-receptor cAMP- dependent mechanisms and augments neointimal proliferation due to NPY and injury. We will determine 1) if injury up-regulates NPY Rs and down-regulates betaARs, and their coupling to AC isoforms and Gs/ialpha, and 2) if this permissive effect of betaARs is NPY-R-specific and depends on betaAR activation or desensitization; and 3) whether transcriptional and/or post-transcriptional mechanisms are involved in the betaAR potentiation of the NPY R expression. The studies will be performed in vitro in rat aortic VSMCs: injured, uninjured, betaAR- transfected, and in vivo in rats, and mice deficient in specific NPY Rs, subjected to angioplasty. BetaAR activation or desensitization will be induced by pre-exposure to beta-agonist, betaAR kinase (betaARK) manipulations or stress (in animals) and altered by beta antagonist and cAMP-Pathway modulators. Cells and animals will be treated with NPY R agonists or antagonists or antisense D-oligonucleotides, and expression of NPY Rs, betaARs, Gs/i, betaARK and beta-arrestin (mRNA and protein), and betaAR-stimulated cAMP levels will be determined. These studies will address clinically relevant issue of whether or not betaAR activation and/or desensitization, such as in stress, heart failure and angina, primes vessels for vascular growth by activating specific NPY Rs and cAMP-dependent signaling, and if so, could open new avenues for prevention ov vascular diseases.